The present invention is related to motors. More particularly, the present invention is related to a snap-on fan cover for use within an enclosed motor.
In certain applications, it is desirable to utilize an electric motor which is totally enclosed. Small electric motors, such as those used in refrigeration and air conditioning units, typically include a stator, a rotor and a frame or housing. The stator assembly typically includes a stator core and one or more windings disposed thereabout. The rotor includes a shaft rotatably mounted within the stator. The shaft is supported by bearing assemblies, and extends in a longitudinal direction through the motor. The stator, rotor, bearings and intermediate portions of the shaft are housed within the frame. An end shield is attached to opposite ends of the frame to enclose the motor.
To cool the motor, a fan is mounted to one end of the rotary shaft, adjacent the end shield. The fan creates an air flow about the exterior of the frame. To protect the fan blades from damage, a fan cover is placed about the fan. The fan draws ambient air through the fan cover and directs it about the motor frame.
During assembly of the motor, the frame may be placed on end, such that the longitudinal axis of the motor is substantially vertical to the assembly work station. This enables the assembler to easily attach the end shield to the frame, and the fan to the rotary shaft. The fan cover can then be positioned about the fan. During this assembly, several features are particularly advantageous. For example, it is desirable that the fan cover be quickly and easily connected to the motor. A typical fan cover may be bolted or screwed to the frame or end shield. In this type of arrangement, a substantial amount of assembly time is required. Each bolt or screw is installed and the motor is turned on its side and/or rotated to access each successive bolt. The time required to install the fan cover can be costly in a high volume production setting. Furthermore, the necessary associated hardware can be expensive, and difficult to handle.
Another concern during assembly is determining proper rotational alignment of the fan cover to the end shield. In certain arrangements where the fan cover is bolted or screwed in place, there is no mechanical means of determining proper alignment. Instead, the fan cover is positioned by visually aligning the bolt holes in the cover to the holes in the frame or end shield. This takes time. A fan cover which includes a mechanical aid to determine rotational alignment of the cover to the end shield or frame would thus ease and quicken assembly.
While fan covers which are bolted to the frame or end shield may not be efficient, they do generally securely fasten the cover to the frame. This feature is beneficial for at least two reasons. First, a strong engagement ensures that the fan cover will protect the fan from damage, and limit the flow of debris through the fan blades. Second, a tight fit between the fan cover and motor frame or end shield limits the effects of vibrational forces. During operation, the fan cover may tend to vibrate with respect to the frame. This may cause the cover to audibly rattle and, over time, loosen.
An object of the present invention is to provide a motor which utilizes an improved fan cover which can be attached to the end shield in a quick and easy manner.
Another object of the present invention is to provide a motor which utilizes an improved fan cover which ensures and facilitates proper rotational alignment between the cover and the end shield during assembly.
A further object of the present invention is to provide a motor which utilizes an improved fan cover which is securely fastened to the end shield.
A still further object of the present invention is to provide a motor having an improved fan cover which is resistant to the effects of vibrational forces.
These and other objects are attained in a motor having a stator and rotor housed within a frame. The rotor includes a rotary shaft, which extends outside of the frame. An end shield is attached to each end of the frame, enclosing the motor. A fan is attached to one end of the rotary shaft, and is used to cool the exterior of the frame. A fan cover substantially surrounds the fan, and is snap-fit to the end shield.
The end shield includes a front face and an annular face having a plurality of receiving slots therein. Adjacent each slot is a boss. The boss includes an inclined ramp leading to the slot. Adjacent the ramp, on opposite sides thereof, the boss includes bearing surfaces which are substantially coplanar to the front face of the end shield. The boss also includes opposing top surfaces which are substantially coplanar to the annular face of the end shield.
The fan cover includes an exterior surface with a vent therein, and an annular rim surrounding the periphery of the exterior surface. Mounting brackets are spaced apart on the annular rim, and allow the fan to be attached to the end shield. Each bracket has a projection thereon which is receivable within the slot on the end shield. The bracket also includes a pair of backstops, each having a stop surface. Each stop surface includes a crushable rib thereon, which is deformable when subjected to a load.
The fan cover can be snap-fit onto the end cover for easy assembly. The cover is positioned such that the projections on the brackets are aligned with the ramp on the boss. In this position, the projection is locked between the ramp sidewalls, limiting rotation of the fan cover with respect to the frame. The cover is pushed onto the frame until the projection is received within the slot. The bearing surfaces on the boss contact and crush the ribs on the stop surface. In this manner, a friction fit between the fan cover and the end shield is achieved.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.